The alkylation of aromatic compounds with aldehydes and ketones in
the presence of a variety of metal cation-exchanged montmorillonites
(Mn+-mont;
Mn+ = Zr4+,
Al3+, Fe3+, Zn2+, H+,
Na+) has been investigated. Al3+- and
Zr4+-Monts are revealed to be effective as catalysts, while
no reaction takes place with Na+-mont.
Al3+-Mont-catalysed alkylation of phenol with several
aldehydes produces mainly or almost solely the corresponding
gem-bis(hydroxyphenyl)alkanes (bisphenols) in good yields, while that
with several ketones affords selectively the corresponding alkylphenols
in moderate to good yields. The alkylation always occurs at the carbonyl
carbon without any skeletal rearrangement and the kind of products
depends much on the steric hindrance of an electrophilic intermediary
carbocation. The alkylation of anisole, veratrole and p-cresol
proceeds well, while that of toluene, benzene, chlorobenzene and
nitrobenzene scarcely occurs.
A beneficial, scalable and efficient methodology for the synthesis of aniline-based triarylmethanes has been established through the double Friedel-Crafts reaction of commercial aldehydes and primary, secondary or tertiary anilines using Brönstedacidicionicliquid as a powerful catalyst, namely [bsmim][NTf2]. This protocol was successfully performed under metal- and solvent-free conditions with a